Work-function anisotropy in noble metals: Contributions from d states and effects of the surface atomic structure

The work functions of high-density Cu and Au surfaces are studied by ab ini tio calculations. We determine the work-function dependence on the crystall ographic orientation of the surface and extract the separate contributions from the s and d states. The face-dependent contributions to the surface di poles from the d states are shown to follow a trend different from that of the s states, which is predicted by Smoluchowski's smoothing argument. The influences on the work function of surface relaxations in Cu and of surface reconstruction for Au(110) are also considered. These effects are explaine d in terms of surface effective charges at relaxed surfaces and by a micros copic model of the charge rearrangement at the reconstructed surface.